US 2012/0262075 A1 discloses a multiple stage sequential current regulator that provides low line current harmonics. Such low line current harmonics result in a relatively low total harmonic distortion, that however may still need to be further reduced.
US20120176826A1 discloses a tapped linear driver wherein the switches S1 to SM are switched off according to input AC voltage. The load group LG1 is not controlled by any switch. A switch S1 is the first one to be switched off and allows current flowing through load group LG1 and LG2.